1. Field of the Invention
The present invention concerns a device and an associated method for generation of a digital x-ray image of a sample.
2. Description of the Prior Art
X-ray image acquisitions of the human breast normally ensue with mammography apparatuses. Medical examinations of the soft tissue of the human breast that in particular serve for early detection of breast cancer can be conducted with x-ray radiation with a mammography apparatus. The breast to be examined is hereby clamped between a subject table and a compression plate that can be displaced against the subject table. An x-ray image acquisition subsequently ensues with a radiation unit fashioned as an x-ray receiver. For this an x-ray detector is typically integrated into the subject table. What is known as soft x-ray radiation in a range below 50 kV is used in the exposure.
Modern mammography apparatuses (for example the MAMMOMAT Novation” by the applicant) possess a base body fashioned as a stand and an angled apparatus arm projecting from the stand, on the free end of which apparatus arm is arranged a radiation source. The apparatus arm is realized as a plate construction and is connected in a rotationally fixed manner with a horizontal rotation axis of the mammography apparatus so that the radiation source can be pivoted by 360° around the isocenter.
The mammography apparatus is typically used for screening examinations in which the exposure unit is located in a 0° position in which the exposure unit and the subject table are arranged opposite one another in the longitudinal direction. Furthermore, the mammography apparatus is also fashioned for a stereo image examination in which the breast is exposed from two different angles, wherein here the exposure unit is pivoted from the rest position by +/−10° or, respectively, by +/−15° around the horizontal axis given a stationary subject table. Furthermore, examinations as tomosynthesis examinations are often also possible with the mammography apparatus, in which the exposure unit travels continuously over a comparably large angle range, for example in an angle range of +/−25° around the horizontal axis given a stationary subject table. Furthermore, an MLO (medio-lateral-oblique) depiction is typically possible. In this examination the exposure unit is normally located at a 45° position, wherein the subject table follows the exposure unit so that subject table and exposure unit are always aligned relative to one another in the same position and at the same distance. The mammography apparatus therefore allows the acquisition of the breast to be examined in standard depictions, for example what is known as the cranio-caudal (CC) or medio-lateral-oblique (MLO) depiction.
The “MAMMOMAT Novation”, in cooperation with the digital biopsy and target acquisition system “Opdima” commercially available from Siemens Healthcare by the applicant, enables a stereotactic biopsy of the human breast. In stereotactic biopsy, a tissue sample of the human breast is extracted and subsequently histologically examined.
For the biopsy the breast is compressed in the mammography apparatus with a compression plate specially fashioned for the biopsy and is fixed in this position. A first x-ray image acquisition (what is known as the overview acquisition) subsequently ensues, via which it is checked whether the tumor or another tissue part to be biopsied lies within a recess of the compression plate.
All following acquisitions ensue in pairs from two different directions, as described above. They are therefore designated as stereo acquisitions. The point in the breast that is to be biopsied is marked from the first stereo acquisition, and from this the required entry position, entry direction and entry depth of a biopsy needles are calculated. The biopsy needle is subsequently inserted into the breast at the calculated point with the aid of a biopsy device, and additional stereo exposures are shot to monitor the position of the needle tip.
One or more samples are then extracted via the biopsy needle. In order to be able to establish whether the correct or, respectively, sufficient samples have been extracted, the samples are examined by means of x-rays. For this the patient must either leave the mammography apparatus so that the sample can be examined in the same apparatus, or an additional x-ray apparatus is provided for an x-ray image depiction of the sample. In the first case, the patient must be repositioned in the mammography apparatus for a possible follow-up examination and an additional biopsy, which entails an increased radiation exposure. In the second case, the stocking of an additional x-ray apparatus incurs additional costs.